Staple drive mechanism for portable pneumatic staplers



. A. G. JUILFS arch 9, 1954 STAPLE DRIVE MECHANISM FOR PORTABLE PNEUMATIC STAPLERS 2 Sheets-Sheei'I l Origlnal Filed Nov. 25, 1949 .WN QLI? mwN vvk,

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Aww.. NWN (W A. G. JUILFS March 9, 1954 STAPLE DRIVE MECHANISM FOR PORTABLE FNEUMATIC STAPLERS 2 Sheets-Sheet 2 Origlnal Filed Nov. 25, 1949 N mv Patented Mar. 9, 1954 STABLE DRIVE MECHANISM FOR PORTABLE PNEUMATIC STAPLERS Albert G. .luilfs, Newtown, Ohio, assignor to Senco Products, Inc., Cincinnati, Ohio, a corporation of Ohio Original application November 23, 1949, Serial Divided and this application August 23, 1950, Serial No. 181,023

18 Claims.

My invention relates to a portable pneumatic stapler primarily for stapling upholstery to the interior of automobile bodies Where the staples must be driven in a conned space, in corners and in crevices, and Where the rapidity of inserting the staples is of great importance. Upholstery, particularly in automobile interiors, is fastened to the Wood framing by two-pronged staples Which must be driven iirmly into the wood of the frame so that the upholstery will not pull loose and Which must be completely driven so that the head or bend of the staple does not project and catch on the clothing of the passengers. Due to the conguration of the interior of the normal automobile, the fabric upholstery is usually fastened in the crevices surrounding the padding and in hidden corners and crevices so that the staples themselves cannot be seen and thus mar the finished appearance of the interior.

rl'his application is a divisional application of my copending application entitled Staple Magazine and Feed Means for Pneumatic Staplers, iiled November 23, 1949, and bearing Serial No. 128,941.

Reference is also made to my copending applications as follows: Staple Feed Mechanism for Portable Pneumatic Stapler led of even date herewith and bearing Serial Number 181,024; Staple Driving Means for Portable Pneumatic Stapler led of even date herewith and bearing Serial Number 181,025; and Valve Control System for Portable Pneumatic Stapler iiled of even date herewith and bearing Serial Number 181,026.

While my novel portable pneumatic stapler is primarily for use in fastening the upholstery on the interior of automobiles, it, of course, may be used for fastening upholstery on furniture as Well, and in any other eld where the driving of staples rapidly and in relatively large quantities is of importance.

It is an object of my invention to provide a portable pneumatic stapler which will fully drive a staple whether the gun is normal to the surface receiving the staple or at an angle thereto. It will also drive a staple completely into the molding or frame, even with the tip of the stapling gun slightly spaced from the material or frame.

It is a further object of my invention to provide a stapler, which while driving the staple completely into the supporting frame, does not cut f or mar the textile material or upholstery being fastened to the frame.

Another object of my invention is to provide a portable pneumatic stapler which is convenient to transport and handle and which is almost foolproof in operation and avoids any chance of misre upon the pulling oi the trigger, and which signais the emptying of the staple carrier by making the action of the stapling gun inoperative.

A further object of my invention is to provide a pneumatic stapler which may be quickly and easily disassembled in order to remove a damaged staple or to repair or replace the staple driving slide Without the necessity of any complicated tools or manipulation.

Another object of my invention is to provide a portable pneumatic stapler having all of the above advantages, but Which is compact as to the gun itself and the track carrying the load of staples, but which holds and drives a great many staples, thus permitting the continual use of the staple gun before the necessity of reloading.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain construction and arrangement of parts of which I shall now describe an exemplary embodiment.

Reference is now made to the drawings Which form a part thereof and in which:

Figure 1 is a front elevation of my novel pneumatic stapler,

Figure 2 is a longitudinal cross section of my novel stapler taken on the section line 2--2 of Figure 1,

Figure 3 is a plan View of my novel stapler With a portion broken away to show a part of the interior,

Figure 4 is a cross section of the nose of my stapler taken on the section line 4-4 of Figure 2,

Figure 5 is a cross section of the driver chamber of my novel stapler taken on the section line 5 5 of Figure *2,

Figure 6 is a sectional view taken on the line 6-6 of Figure 2,

Figure 7 is a rear elevation of my novel stapler,

Figure 8 is a cross section of my stapler with the piston, rod, and staple driver in its final position after driving a staple and taken on the section line 8-8 of Figure 7,

Figure 9 is a cross section of the staple feeder latch taken on the section line 9 9 of Figure 8,

Figure 10 is a cross section of the end of the staple track and staple receiving slot with the staple moving shoe in the empty position,

Figure ll is a plan view of the piston rod and staple driver slot,

Figure 12 is a perspective view of the removable closure portion of the slot housing, and

Figure 13 is a plan View of the end of the piston rod and the staple slide used in my stapler.

Briey in the practice of my invention, l provide a portable pneumatic stapler which consists of a pneumatic cylinder carrying a free sliding piston. A piston rod contacting but disconnected to the piston runs from the interior of 'the cylinder to a staple driver which is mounted in a slot in which each individual staple to be driven is positioned by means of the staple feeder.

The inlet aperture for the compressed air enters the cylinder at a position below the head of the cylinder and is covered by the piston when at rest. There is a small groove in the cylinder wall which carries the air to the head of the cylinder behind the piston. When air is released to the cylinder, the piston prevents the direct owing of the air through the large inlet aperture, but a small porti-cn news through the groove in the cylinder wall and moves the piston to the left relatively slowly. The piston in turn moves the piston rod and the staple driver up to the staple which is positioned in 'the slot. The proportion l ing is such that after the piston has moved the staple driver into contact with the staple, the relatively large inlet port is uncovered and a large amount or compressed air enters the cylin der behind the piston, urging it rapidly to the left. This action drives the staple along the slot and out the nose of the gun. The piston moves rapidly to the left and the air before it exhausted through a port in the cylinder wall. As the piston passes the port, a resilient air cushion is set up between the piston and the forward end of the gun. This prevents the piston from contacting the end of the cylinder too hard and stops its movement. Since the piston rod is not fastened to the piston itself, its inertia carries it beyond the point where the piston stops and the end of the staple driver is projected slightly beyond the nose of the slot, thus insuringr the driving home of the staple, even if the nose of the gun is slightly spaced from the fabric frame.

In the handle of the stapler, I provide an air chamber of appreciable size which permits the building up of the volume of the compressed air prior to its release into the cylinder. This permits the use of relatively small air lines thus making the stapler easier to use.

The staples themselves are loaded on a track which, in this instance, is formed as a portion of the circumference of a circle. I provide an arm which projects radially from the track and inwardly to a center point on the body of the gun and which is urged towards the row of staples by means of a piston actuated by compressed air feeding from the chamber in the handle and controlled by a valve. The piston forces the arm and the foot mounted on the end of the same which rides in the track behind the rearwardmost staples to the left of the drawings, thus pushing the rst staple up into the siot in the front of the driver. the staple leaves the slot and the staple driver is withdrawn, the following staple takes its place. When the last staple has been driven, there is an ear on the shoe which follows the staples, which slips up into the slot and prevents the staple driver from further movement to the left and in effect jamming the gun, thus indicating to the operator that there are no more staples on his track.

Referringr to the drawings, I provide a cylinder I in the body housing 2 of my portable stapler. Within the cylinder I is a piston 3 which is at rest against the cylinder head 4 when the stapler is not in operation.

A piston rod e runs out of the cylinder I into a slot S and is urged against the piston 3v by a helical spring which is based in a slidable collar or retaining cup 8. On the end of the piston rod 5 is mounted a staple driver 3. The staple driver s has a hole on one end which slips over a boss I on the end of the piston rod 5. The driver S reciprocates in a slot I I provided in the lower nose member I3a of the nose I3. The slot extends through the nose as indicated at I2.

An inlet port I4 runs from the trigger valve 55 to the cylinder wall I. rThe port I4 is located a predetermined distance from the cylinder head 4 and is covered and sealed by the piston 3 when the piston is in its operative position, as shown in Figure 2. A narrow groove I5 (see also Figure 6) runs from the port I4 to the head d of the cylinder I, and I preferably provide an annular opening I6 around the head l to permit the small amount of air passing through the groove I5 to flow behind the piston 3.

In the wall of the cylinder l an appreciable distance from the opposite end of the cylinder, I provide an exhaust port I'. This exhaust port I permits the air in the cylinder I to escape as the piston 3 moves to the left. However, when the piston 3 slides over and seals the port I', a resilient cushion of air is built up between the piston 3 and the forward end of the gun is blocked by the cup 8. This cushions further movement of the piston 3.

In the handle Il of the stapler there is provided a relatively large air chamber I8 which permits the compressed air iiowing into the handle from the connection I3 to build up in volume.

When the trigger 55 is actuated and moved to the position shown in Figure 8, air flows from the chamber I8 through the passageway Ill. Since this passageway is sealed by the pist-on 3, the air does not directly ow into the cylinder from the port la. However, a small amount fiows through the groove I 5 and into the annular space I6 behind the piston 3. This moves the piston 3 at a relatively .slow rate to the left in Figure 2.

A staple has been fed into the slot II by the staple feeder at a spot 2E! just ahead of the staple driver 9. The distance between the port I4 and the cylinder head 4 is approximately the same distance as the @nd 9 of the driver 8 from the point 2D where the staple rests in the slot Il. From this, it is apparent that when the piston 3 moves relatively slowly to the left pushing the piston rod 5 and the staple driver 9 to the left, this slow movement is of a distance sufficient to pick. up the staple. This relatively slow pick up prevents jamming. At this point, the piston 3 has uncovered the port I6 which permits a relatively heavy inrush of compressed air behind the piston 3. This drives the piston 3 to the left and the air in the cylinder before it exhausts through the port l. The piston rod 5 and staple driver S m-ove rapidly to the left, driving the staple out of the nose of the gun and into the work. The piston 3 is stopped by the resilient cushion of air built up between it and the forward end of the gun after the piston 3 has healed the port i A washer 2| is provided in the forward end of the cylinder l to assist in stopping the piston 3. However, the piston 3 is substantially stopped by the cushion of air before it reaches the washer 2l. This cushion of air is built up when the piston 3 blocks the port I1 and when the rod 5 has advanced so as to substantially ll that orifice in the cup 8 through which it just nicely slides, all as best seen in Figure 8. Air trapped between the piston 3 andthe forward end of the gun, as closed by the cup 8 and 1nd 5, provides, the desired cushion. Although some of the trapped air may leak out around the rod 5 through the orice in cup 8 as the piston 3 advances, a substantial cushioning aect is still obtained because that volume of air moved forward by the piston 3 is quite large relative to whatever volume there is that could possibly escape around the rod 5 as above described. The inertia of the piston rod 5 carrying the driver 9 is such that it carries on after the rod 5 leaves the piston 3, as shown in Figure 8. This permits the end 9 of the driver to project beyond the nose I3 of the stapler. The spring 'I limits this movement of the piston rod 5 and also drives the piston rod 5 and the piston 3 back to its home position, as shown in Figure 2 when the air within the cylinder I exhausts through passageway I4, the trigger mechanism I5, and the exhaust passageway 22.

The cushioning of the piston 3 by means of the air compressed by it against the forward end of the gun prevents the piston 3 from hammering against the end of the cylinder and thus injuring the gun.

Occasionally, a defective staple gets into the slot I I of the gun or a staple may become jammed therein. In order to permit the removal of such a defective staple, I provide a removable closure 23 in the staple driveway surrounding the slot I I. This closure 23 contains a rounded portion 24 which slides under a part of the body 2 of the gun and abuts the spring retaining cup 3. The other end 25 of the closure 23 is wedge-shaped and snaps into a complementary aperture in a part of the nose I3, as is shown in the solid lines in Figure 2. When it is desirable to remove a defective or jammed staple, the closure 23 is moved to the right (as viewed in the vari-ous figures) against the tension of the spring l. This may be done by inserting a tool 25 in two holes 2l in the closure 23 and pushing on the tool with the nger. In the event the staple driver 9 should become bent or injured, it may be easily removed by pushing the closure 23 to the right (as viewed in the various figures) and lifiting the end 25 up and out from under the aperture in the nose I3, as is I shown in the broken lines in Figure 2. In this position, the closure 23 may be completely removed. This exposes the driver 5 which may be easily lifted out of its track and a new driver 5 inserted in its place. Figure ll shows the slot II in which the driver 5 operates and this is made available when the closure 23 is removed.

One of the members forming a part of the nose I3 is indicated at I3a in Figure 2. This member I3a is shown in detail in Figures 5 and 1l. As shown in these figures, the member I3a is channeled or grooved so as to provide the slot Il in which the staples are positioned and driven. The bottom of this slot is indicated at Ila in the forward end of the nose member I 3a as shown in Figure 11.

Also, as is shown in Figures 5 and ll, the member Ia is provided with a pair of ledges 13b downwardly offset from the upper surface thereof. These ledges project inwardly from the side walls which denne the slot II. It is on these ledges lSb that the staple driver S rides, see especially Figure 5. As also shown in this gure, the closure member 23 rests on the upper surface of the nose member I3a, the staple driver just nicely sliding therebeneath on the ledges i317.

The closure member 23 is provided with a slot 23a (see Figure 5) which just nicely receives the piston rod 5 when it is advanced as above described. It'should be noted that the' side walls of this closure member 23 are quite thick; these side walls extend inwardly to such an extent that they completely overlie the ledges I3b. When a staple is brought flatwise into the slot II, at the point generally indicated at 20 in Figures 2 and 1l, this point being ahead of the forward ends of the ledges I3b, it comes into contact with the bottoms of the side walls of the closure member 23; i. e., the grooved closure member 23 limits upward movement of the staples. Thus when the driver 9 slides forwardly on the ledges I3b beneath the closure member 23, the piston rod at this time sliding within the groove 23a, it will contact the staple then in the groove II. This staple will be driven from beneath the closure member, against which it is initially maintained as above set forth, across the bottom Ila, beneath the upper member of nose I3, and ejected from the gun as at I2.

The above is a description of the mechanism of the stapler which actually drives the staple. 'I'he trigger mechanism 55 is a valve of the usual type and its sports and operations which insure its actuation and permit the exhaust of the cylinder -l is believed completely clear from the drawings, Figures 2 and 8. The connection I9 for the hose is preferably of a swivel type as shown in the drawings, thus permitting the easy manipulation of the stapler' by the operator. The mechanism if necessary, may be easily serviced by removal of the parts and particularly the cylinder head 4 which is screwed into the body, as shown in the drawings. The control of the trigger 55 is maintained by a spring I5' which insures the return of the trigger to the position shown in Figure 2 for exhausting through port I4 when the 'finger is removed or relaxed.

A particularly important feature of my invention is the provision of the small groove I5 be tween the inlet port I4 and the cylinder head 4. By making this groove extremely small, such as ,008 inch, I insure that the air Will quickly ow through the groove I5 and insure the movement of the piston 3 at once. In other words, it is almost impossible to pull the trigger 55 so slowly as to permit the air to leak in behind the piston and fail to build up a moving pressure. The movement of the air through the groove I5 insures that the groove I5 remains perfectly clean and unclogged at all times. The clogging of this groove is further prevented by the movement of the piston which together with the groove forms a hole. the piston side of which is opened upon every movement of the piston.

The operation of the valve means is as follows. Air is admitted to the stapler as indicated at I9 in Figures 2 and 8. In Figure 2 the ytrigger valve 55 is shown in its normal or closed position. In this position the spring I5 maintains the valve 55 in the left hand (as viewed in Figures 2 and 8) portion of the sleeve 5,6 within which this valve slides. When this valve is so maintained the port 51 in the sleeve 56 is unobstructed and the member 58 blocks the sleeve 55 so as to prevent air, from the chamber I8, reaching the port I4. This is the exhaust position. Thus air, which is between port I' and cylinder head 4, is exhausted, on movement of the piston 3 towards the head 4, through port I4 (and I5) around the valve plunger 59, through the port 57 and into the exhaust passage 22 in the handle I l.

Movement of the valve 55 against the spring I 5' has the following efect. The body of the valve 55 blocks the exhaust port 5l and the member 58 is moved off the end of sleeve 56. Air then enters theport I4 around the valve member 5B.

This airv cannot bypass the port I4 and exit 'through the exhaust port 51 because this latter 'port is blocked by the body of valve 55, as is clearly shown in Figure 8. A small amount of air then passes through the small channel l5 and gathers behind piston 3. The piston is thereby slowly moved to the left until the port i4 is e posed at which point the bulk of the air enters behind piston 3 and moves it rapidly to the left. When the piston 3 moves past the port l' it is stopped by a cushion of air as above described.

I will now describe a staple feeding means which may be employed with my novel stapler.

Referring to Figure 2, a staple track 28 is attached at one end to the nose i3 of my gun and is curved, as shown in the drawings so that the other end 29 may be attached to the handle H of the gun. The operative portion of the track 28 conforms to a portion of the circumference of a crle. The track 28 is substantially square in cross section and contains a guard 36 spaced therefrom to hold the staples in a straddling position around the track 28. xEhe curved track 28, in combination with the extended nose i3, makes possible the use of my staple gun in conned quarters unaccessible to staple guns now known to me.

At a point 3l, which represents the center of the circle of which the track 28 is a portion oi' the circumference, I mount an arm 32 by means of a pintle at 3l. from the center 3| to the track 2S and is terminated by a shoe 33. which is in the form of a staple in cross section and which rides on the track 28 under the guard 36. As is apparent from Figure 2, the shoe 33 may be withdrawn to the right out from under the guard 33 to permit the loading of a row of staples on the track 28. Thereupon, the shoe 33 is positioned behind the Y last staple and under the guard 3B, as shown in Figure 8.

In the body 2 of the gun and adjacent the point 3| to which the arm 32 is pivoted, I provide a cylinder 34 carrying a piston 35'. There is a passageway 36 leading from the end of the cylinder 34 through a valve to a passageway 31 which is open to the chamber I8.

A yoke 33 pivoted to the arm 32 loops over the end 39 of the piston 35 and rides in a slot 4i) where it is held by a pin 4l. From the alcove, it is apparent that when air is permitted to flow in the passageway 35, the piston is moved to the left as shown in Figure 8 and the arm 32 is pulled to the left, thus forcing the shoe 33 against the row of staples which in turn forces the foremost staple into the slot l l. By this means a continual pressure is exerted on the row of staples at all times during the operation of the gun when the valve 42 is in the position shown in Figure 9.

When the last staple has been driven, the leading edge 43 (see Figure 2) of the shoe 33 enters into the slot Il, abuts against the bottoms of the side walls of the closure member 23, and is held in this position. This prevents the driver 9 from moving to the left and, in effect, jams the gun so the operator will know that he is out of staples. The position of the edge 43 of the shoe in the slot I l is shown in Figure 10. When this condition is reached, the operator actuates the valve 42 which permits the air in the cylinder 35 to exhaust through the passage 36 and out through the clearance 44. This permits the return of the arm 32 with its follower Shoe 33 to the position shown in Figure- 2 by hand so the track 28 may be 'again loaded with a new supply of staples.

The arm 32 projects radially Y A cross sectional view of the valve42 is shown in Figure 9 and is believed clear, The port 33 is shown and the port 45 is shown, which runs through the body 2 of the gun to the passageway 31 and then to the chamber I8, as shown in Figure 2. Fixed between the valve members 42 is a cylindrical member 60 of smaller diameter than the bore 6 I Within which it and the members 42 slide. On either side of the member 6D are gaskets 62. When the valve members 42 are in the position shown in Figure 9, the operative position of the valve, air passes from the chamber I8 into the passageway 31, through the conduit 45, around the member 30, into the passageway 36 and into the cylinder 34, whereby the piston 35 is moved to the left (Figure 8) and the shoe 33 with it (through the yoke 38 and arm 32) When the valve members 42 are moved to a position the reverse of that shown in Figure 9 the passageway 31 is blocked or cut off from the passageway 33 by one of the gaskets 62. This gasket will have cleared the passageway 3B 50 that air may bleed from this passageway around the reduced portion 44 of one of the members 42 and out of the gun. The arm 32 may then be returned to the position of Figure 2 as above described.

In actual practice, the tool 26 which is used to slide or remove the closure 23 is removable so there is no danger of its catching on trim and thus opening the closure 23 inadvertently.

From the above, it is apparent that I have provided a portable pneumatic stapler which is very sure in its operation and which drives a staple completely home without tearing the fabric and which is operable from almost any reasonable position. The nose is very slender so that it can be slid into small crevices and corners between the upholstery and molding or an automobile interior.

While in the above description and drawings I have described and shown a stapler and a feed therefor, it is to be understood that my stapler may be used for driving nails or brads, or with slight modication, for setting rivets.

While I have shown a feed, the arm of which is operated pneumatically, it may be preferable in some cases to operate the arm by means of a coil spring or the like. The provision of the track congured as a portion of the circumference of. a circle insures a smooth and even flow of staples. accommodates a great number of staples, and yet conforms relatively closely to the configuration of the gun itself.

My stapler is compact and light and may be easily adjusted or repaired. Itis extremely simple to remove jammed staples. and, if necessary, the cylinder head may be quickly removed and the interior of the cylinder exposed. The groove running from the main vent to the rearv of the piston is self-cleaning due tothe movement of the piston over the groove.

It is to be understood that modifications may be made in my invention without departing from the spirit thereof and I do not intend to limit myself otherwise than as pointed out in the claims which follow.

Furthermore, although I have disclosed many novel features of staple gun construction in combination with one another-for the purpose of setting forth a full and complete disclosure of an operative staple gun-it should be noted that many of these features may be used independently. Thus the particular staple drive mechanism herein set forth and claimed may be used with.

for example, feed mechanisms other than that herein described.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder having an axial recess in its lower face, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, staple driving means freely moveable axially of said piston and having a portion to be received in said axial recess in said piston, a spring urging said staple driving means towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driving means, a closure member cooperating with said groove, and means for feeding staples against said closure member and in front of said staple driving means whereby on movement of said piston away from said cylinder head said staple driving means will contact a staple positioned against said closure member and drive same before it through said groove.

2. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from sai-d head, staple driving means freely moveable axially of said piston, a spring urging said staple driving means towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driving means, a closure member cooperating with said groove, and means for feeding staples against said closure member and i in front of said staple driving means whereby on movement of said piston away from said cylinder head said staple driving means will contact a staple positioned against said closure member and drive same before it through said groove, said compressed air introducing means including a relatively large inlet vent located in the wall of said cylinder and which is closed by the piston when said piston is against said cylinder head and a small longitudinal groove in said cylinder wall running from said vent to said cylinder head, said staple feeding means including an opening through which the staples are delivered ahead of the staple driving means, and said longitudinal groove being of approximately the same length as said opening, whereby initial movement of a staple driven by said staple driving means is relatively slow compared to the succeeding movement when the piston has moved past said relatively large inlet vent.

3. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, staple driving means freely moveable axially of said piston, a spring urging said staple driving means towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driving means, a closure member cooperating with said groove, and means for feeding staples against said closure member and in front of said staple driving means whereby on movefi t) ment of said piston away from said cylinder head said staple driving means will contact a staple positioned against said closure member and drive same before it through said groove, said compressed air introducing means including a relatively large inlet vent located in the wall of said cylinder and which is closed by the piston when said piston is against said cylinder head and a small longitudinal groove in said cylinder wall running from said vent to said cylinder head, said staple feeding means including an opening through which the staples are delivered ahead of the staple driving means, and said longitudinal groove being of a length at least as great as the distance between the driving end of said staple driving means and said opening when said piston abuts said cylinder head, whereby movement of the staple driving means to a staple fed through said opening is relatively slow compared to the succeeding movement when said piston has moved past said relatively large inlet vent.

4, The stapler of claim 3 in which said staple feeding means includes a staple follower, said staple follower having a portion which extends through said opening into the path of said staple driving means when no more staples remain in the staple feeding means, whereby said staple driving means will contact said staple follower portion and jam the gun to warn an operator of the lack of staples, said staple driving means contacting said staple follower portion during its period of relatively slow movement whereby sheering of the staple follower portion by the staple vdriving means is avoided.

5. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, staple driving means freely moveable axially of said piston, a spring urging said staple driving means towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driving means, a closure member cooperating with said groove, and means for feeding staples against said closure member and in front of said staple driving means whereby on movement of said piston away from said cylinder head said staple driving means will contact a staple positioned against said closure member and drive same before it through said groove, and means to cushion the driving stroke of the piston comprising an outlet vent located towards that end of said cylinder which is opposite said cylinder head and which outlet vent is closed before the end of the driving stroke.

6. The stapler of claim 5 in which said outlet vent is closed by said piston.

7. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, staple driving means freely moveable axially of said piston, a spring urging said staple driving means towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driving means, a closure member cooperating with said groove, and means for feeding staples against said closure member and in front of said staple driving means whereby on movement of said piston away from said cylinder head said staple driving means will contact a staple positioned against said closure member' and drive same before it through said groove, said staple driving means including a driving blade fixed to another member which normally seats within a recess provided axially of said piston.

8. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into. said cylinder near said head whereby said piston is moved away from said head, staple driving means freely moveable axially of said piston, a spring urging said staple driving means towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driving means, a closure member cooperating with said groove, and means for feeding staples against said closure member and in front of said staple driving means whereby on movement of said piston away from said cylinder head said staple driving means will contact a staple positioned against said closure member and drive same before it through said groove, said nose structure including a second member, means fixing said second nose member to said grooved nose member, a retaining cup slideable in said stapler, said spring abutting said retaining cup, and said closure member having a iirst portion which is adapted to abut said retaining cup and a second portion which abuts said second nose member whereby said closure member is wedged between said second nose member and said retaining cup, said closure member being removeable from said stapler by forcing said first portion against said retaining cup and said spring until said second portion clears said second nose member.

9. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder having an axial recess in its lower face, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, a staple driver freely moveable axially of said piston, whereby said staple driver may advance by inertia after said piston reaches the end of its stroke, means on the driver adaptn ed to be received in said axial recess in said piston, a spring urging said staple driver towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driver, and means for feeding staples into said groove in front of said driver whereby on movement of said piston away from said cylinder head said staple driver will contact a staple positioned in said groove and drive same before it through said groove.

10. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, a staple driver freely moveable axially of said piston, a spring urging said staple driver towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including aY member having a groove adapted to receive said staple driver, and means for feeding staples into said groove in front of said driver whereby on movement of said piston away from said cylinder head said staple driver will contact a staple positioned in said groove and drive same before it through said groove, said nose structure including a second member fixed to said grooved member and a closure member cooperating with said groove, said closure member having a portion lockingly engageable with said second member and being positioned to be acted upon by means including said spring whereby said closure member is wedged by the force of said spring and said second member, said closure member being removeable from said stapler by urging said closure member against the action of said spring until said locking portion is disengaged from said second member.

11. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, a staple driver freely moveable axially of said piston, a spring urging said staple driver towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driver, and means for feeding staples into said groove in front of said driver whereby on movement of said piston away from said cylinder head said staple driver will contact a staple positioned in said groove and drive same before it through said groove, and means to cushion the driving stroke of the piston comprising an outlet vent located towards that end of said cylinder which is opposite said cylinder head and which outlet vent is closed before the end of the driving stroke.

l2. A portable pneumatic stapler comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, a staple driver freely moveable axially of said piston, whereby said staple driver may advance by inertia after said piston reaches the end of its stroke, force transmitting means on said driver and said piston having telescopic engagement, a spring urging said staple driver towards said piston and said piston against said cylinder head, nose structure for said body, said nose structure including a member having a groove adapted to receive said staple driver, and means for feeding staples into said groove in front of said driver whereby on movement of said piston away from said cylinder head said staple driver will contact a staple positioned in said groove and drive same before it through said groove.

13. In an apparatus for driving staples: a staple driver; means to urge said driver in a staple driving direction; means to feed staples to a position before said driver whereby each successive staple is in a position to be driven; the driver urging means comprising a piston in back of said driver and free thereof; valve means for admitting fluid against said piston to move same against said driver; means to stop said piston; separate means to stop said driver whereby said driver is free to advance by inertia after said piston is stopped; and trigger means to actuate said valve means'.V

14. In an apparatus for driving staples; a staple driver; means to urge said staple driver in a.

staple driving direction; means to feed staples to a, position before said driver whereby each successve staple is in a position to be driven; the driver urgingv means comprising a piston havinga 13 recess receiving said driver, said driver being free to move longitudinally of said piston; valve means for admitting fluid against said piston to move same; means to stop said piston independently of said driver; and trigger means to actuate said valve means.

15. A portable pneumaticI tacker comprising a main body, a cylinder in said body, said cylinder having a head, a piston in said cylinder having a recess in its lower face, means to introduce compressed air into said cylinder near said head whereby said piston is moved away from said head, a staple driver freely movable with respect to said piston, means to stop said piston `separate from said staple driverI means on the driver adapted to be received in said recess in said piston, a spring urging said staple driver towards said piston and said piston against said cylinder head, nose structure for said body dening a passageway for said staple driver, and means for feeding staples into said passageway in front of said driver whereby on movement of said piston away from said cylinder head said staple driver will contact a staple positioned in said passageway and drive same before it through said passageway.

16. The tacker of claim 15 in which said means for stopping said piston includes means for providing an air cushion substantially at the end of the driving stroke.

17. The tacker of claim 15 in which said means for stopping said piston includes a resilient pad References Cited in the file of this patent UNITED STATES PATENTS Name Date Randall Dec. 12, 1933 Number 

